The present invention relates generally to a hybrid-type electret condenser microphone, and more particularly to a miniaturized electret condenser microphone for use in portable telephones or information communication devices, in which main components including electronic circuits, such as an IC device and the like, are integrated into a chip.
Korean Patent Publication No. 1993-3063, which was filed on Dec. 22, 1990 in the name of this applicant and issued on Apr. 17, 1993, discloses an electret condenser microphone which is attached to a mike, a telephone, a portable telephone, a video tape recorder, a toy and the like and serves to transform sound pressure into an electrical signal.
The electret condenser microphone disclosed in this patent is schematically shown in FIG. 1 in a cross section. As shown in FIG. 1, the electret condenser microphone includes a case 3 which has an opening 1 formed at a central portion of an underside thereof and a cover 2 attached to an outer surface thereof. A polar ring 4 and a vibratory diaphragm 5 are disposed within the case 3. An amplifier unit 9 is secured to a printed circuit board 12 by means of a soldering 13. An output lead 11 of the amplifier unit 9 is connected to the printed circuit board 12 by soldering. On the vibratory diaphragm 5 is disposed a fixed electrode 16 which is connected to an input terminal 10 of the amplifier unit 9 and insulated by an insulating ring 17. A dielectric plate 20 applied with an electrostatic material is disposed within the fixed electrode 16. In addition, a plurality of openings 21 are formed at a peripheral edge of the fixed electrode 16.
In the conventional electret condenser microphone having a construction as described above, however, the dielectric plate 20 is separately adhered onto the fixed electrode 16 in a state where the fixed electrode 16 insulated from the case 3 by the insulating ring 17 is connected directly to the vibratory diaphragm 5. For this reason, although the electret condenser microphone can be significantly improved in performance, it has a problem in that it cannot be miniaturized. Another problem is that the contact area between the input terminal 10 of the amplifier unit 9 and the fixed electrode 16 is limited, so that inferior electrical contact occurs between the input terminal 10 of the amplifier unit 9 and the fixed electrode 16 and hence production yield cannot be increased.
Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art, and an object of the present invention is to provide an electret condenser microphone which can be miniaturized.
It is another object of the present invention to provide an electret condenser microphone which can be manufactured in increased yield.
To accomplish the above objects, the present invention provides an electret condenser microphone which comprises: a case which is electrically grounded and has an opening formed at an upper side thereof and a plurality of sound holes formed at a central portion thereof, the sound holes serving to collect and pass sound there-through; a vibratory diaphragm which is disposed within the case in parallel to an inner bottom surface of the case, apart from the bottom surface of the case at a given distance (xcex94t), and which is vibrated by sound pressure coming in through the sound holes of the case so as to transform a sound signal into an electrical signal; a vibratory diaphragm support member which is disposed on the vibratory diaphragm and has a concave groove formed at an outer surface thereof and a concave portion, the concave groove being formed such that the vibratory diaphragm is spaced apart from the vibratory diaphragm support member at a given distance, the concave portion having a plurality of small sound holes formed at a bottom surface thereof such that the vibratory diaphragm is easily vibrated; an integrated circuit which is attached to the vibratory diaphragm support member and serves to amplify the electrical signal; an insulating cap which covers the opening formed at the upper side of the case while electrically insulating the vibratory diaphragm support member from the case; a first contact pin which is disposed on the insulating cap such that it receives the amplified signal from the integrated circuit attached on the vibratory diaphragm support member through a contact element connected by a lead to the integrated circuit and transmits the received signal to the outside of the electret condenser microphone; and a second contact pin which is disposed on the insulating cap such that it receives the amplified signal from the integrated circuit attached to the vibratory diaphragm support member through a contact element connected by a lead to the integrated circuit and transmit the received signal to the outside of the electret condenser microphone.